In 1806, during a campaign in which he shattered the myth of Prussian military invincibility, Napoleon sat down in his bivouac to deal with a matter that could wait no longer. "I charge you exclusively with the surveillance of the Opéra," he wrote to a minister in Paris. "Let severe discipline reign."

With the Prussians broken on the fields of Jena and Auerstadt, the emperor turned to crush the tsar's army - but further stern guidance about intrigue at the Opéra was sent back to France, this time to his chief of secret police: "If it doesn't cease, I will give them un band militaire which will make them march with drums beating." Today's Covent Garden types may carp at the cruelty of critics who think they are Napoleon, but those who had to perform for him in person knew the meaning of suffering for their art.

It would be easy to write off the civil aspects of the Napoleonic project as the work of a man who understood only the motions of his military machine but expected everybody else - from divas to dressmakers - to march in step. It would also be glib, as Alistair Horne shows in this book, to set aside the battles and the Grande Armée and ask what difference the "Corsican upstart" made to the everyday lives of those who experienced the Age of Napoleon.

You do not need to delve very deep into the 32 published volumes of Napoleon's correspondence, the four further books of letters "inédites" and the dozens of other collections of his writing to realise there was no matter too insignificant to demand his attention. In varying moods of elation, frustration or exhaustion, he directed everything from the appointment of bishops to the construction of a vast new palace for his son or the promotion of junior officers in insignificant garrisons.

Horne calls Napoleon "the most hands-on leader the world has ever seen", and it is impossible to argue. These qualities have led many to praise Bonaparte as someone possessed of amazing recall and attention to detail. My own view is that the yards of official directives also show the weakness of the imperial system perfectly. He created a web of patronage so potent that many generals or ministers would do nothing unless they knew the emperor in person had commanded it, so for much of the time nothing is precisely what they did.

Plans for universal secondary education - so impressive in early directives - had created only 36 lycées by the time of Napoleon's abdication. Visionnary schemes to turn Paris into a stunning neo-classical metropolis had also, in fact, transformed just a few streets by 1815 and Waterloo. Perhaps there weren't enough secret police to intimidate the pedagogues and town planners as well as the Opéra.

Horne points out that the arts "wither in a climate of despotism", charting how theatre and newspapers were smothered by censorship. French creativity between 1800 and 1815 found other forms, and he writes brilliantly about the delicacies served in Parisian restaurants or the fashions flaunted by Josephine de Beauharnais.

Napoleon's era amounted, of course, to something more than empire line dresses or indeed liberation from underwear. To Horne, the Code Napoleon - his canon of law - was the "most solid and enduring achievement" of his rule. This produced equality of justice, even if it didn't deliver the liberty or fraternity promised by the revolution.

Horne is at his strongest when sampling the spirit of the age through the eyes of its great writers. The words of Hugo, Stendhal or Byron are deployed with dizzying learning - always germane, always enlightening. He finds inspiration in all sorts of places - even, for example, a Napoleonic forerunner of the Michelin restaurant guide, where the recipe for a perfect leg of lamb involves it being "beaten like a thief".

Even those of us who think we know something about the period will find many delightful surprises. The author introduces us to Vivant Denon, a diplomat and artist who "accompanied Napoleon on almost all his campaigns ... tireless in seeking out and cataloguing artefacts for transportation to Paris ... with total indifference to the humiliation of the subject nations that were being robbed".

As Denon delivered the results of this pillaging to the Louvre, he too received numerous directives from his master about how the art should be hung, the galleries heated or the times for public access extended. Napoleon's involvement in such questions as museum opening hours is fascinating because it shows how his conception of "la gloire" drew ordinary people into the idea that he was making France great.

His weakest suit was economics. There are a few references to financial crises and to England's blockade, but never a satisfying connecting narrative that explains why visitors to France in 1814 who had not seen the country for years were shocked at how impoverished it had become, or why so many of Napoleon's big ideas were hamstrung by the underlying economic malaise.

Perhaps, though, Napoleon himself would deride such preoccupations as typical of an English shopkeeper, and appreciate Horne's narrative as closer to the spirit that animated his great project. What matter a few thousand francs (or indeed lives) when one has assembled the world's greatest art at the Louvre, created its most beautiful capital or dined on its finest cuisine?

In the end, any one of the topics touched on by the author could have made a full book on its own, adding to the vast and still growing literature on this period. Horne's skill lies in boiling down the complexity of so many fields of endeavour away from the battlefield into a series of vivid tableaux, beautifully sketched, that really bring this extraordinary epoch to life. In short, it is the perfect read for someone who asks the question: apart from being a great general, what did Napoleon stand for?

· Mark Urban's Rifles: Six Years with Wellington's Elite is published by Faber